/* ===========================================================
 * JFreeChart : a free chart library for the Java(tm) platform
 * ===========================================================
 *
 * (C) Copyright 2000-2008, by Object Refinery Limited and Contributors.
 *
 * Project Info:  http://www.jfree.org/jfreechart/index.html
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
 * USA.
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
 * in the United States and other countries.]
 *
 * ----------
 * Range.java
 * ----------
 * (C) Copyright 2002-2008, by Object Refinery Limited and Contributors.
 *
 * Original Author:  David Gilbert (for Object Refinery Limited);
 * Contributor(s):   Chuanhao Chiu;
 *                   Bill Kelemen;
 *                   Nicolas Brodu;
 *                   Sergei Ivanov;
 *
 * Changes (from 23-Jun-2001)
 * --------------------------
 * 22-Apr-2002 : Version 1, loosely based by code by Bill Kelemen (DG);
 * 30-Apr-2002 : Added getLength() and getCentralValue() methods.  Changed
 *               argument check in constructor (DG);
 * 13-Jun-2002 : Added contains(double) method (DG);
 * 22-Aug-2002 : Added fix to combine method where both ranges are null, thanks
 *               to Chuanhao Chiu for reporting and fixing this (DG);
 * 07-Oct-2002 : Fixed errors reported by Checkstyle (DG);
 * 26-Mar-2003 : Implemented Serializable (DG);
 * 14-Aug-2003 : Added equals() method (DG);
 * 27-Aug-2003 : Added toString() method (BK);
 * 11-Sep-2003 : Added Clone Support (NB);
 * 23-Sep-2003 : Fixed Checkstyle issues (DG);
 * 25-Sep-2003 : Oops, Range immutable, clone not necessary (NB);
 * 05-May-2004 : Added constrain() and intersects() methods (DG);
 * 18-May-2004 : Added expand() method (DG);
 * ------------- JFreeChart 1.0.x ---------------------------------------------
 * 11-Jan-2006 : Added new method expandToInclude(Range, double) (DG);
 * 18-Dec-2007 : New methods intersects(Range) and scale(...) thanks to Sergei
 *               Ivanov (DG);
 *
 */

package net.droidsolutions.droidcharts.core.data;

import java.io.Serializable;

/**
 * Represents an immutable range of values.
 */
public strictfp class Range implements Serializable {

	/** For serialization. */
	private static final long serialVersionUID = -906333695431863380L;

	/** The lower bound of the range. */
	private double lower;

	/** The upper bound of the range. */
	private double upper;

	/**
	 * Creates a new range.
	 * 
	 * @param lower
	 *            the lower bound (must be <= upper bound).
	 * @param upper
	 *            the upper bound (must be >= lower bound).
	 */
	public Range(double lower, double upper) {
		if (lower > upper) {
			String msg = "Range(double, double): require lower (" + lower
					+ ") <= upper (" + upper + ").";
			throw new IllegalArgumentException(msg);
		}
		this.lower = lower;
		this.upper = upper;
	}

	/**
	 * Returns the lower bound for the range.
	 * 
	 * @return The lower bound.
	 */
	public double getLowerBound() {
		return this.lower;
	}

	/**
	 * Returns the upper bound for the range.
	 * 
	 * @return The upper bound.
	 */
	public double getUpperBound() {
		return this.upper;
	}

	/**
	 * Returns the length of the range.
	 * 
	 * @return The length.
	 */
	public double getLength() {
		return this.upper - this.lower;
	}

	/**
	 * Returns the central value for the range.
	 * 
	 * @return The central value.
	 */
	public double getCentralValue() {
		return this.lower / 2.0 + this.upper / 2.0;
	}

	/**
	 * Returns <code>true</code> if the range contains the specified value and
	 * <code>false</code> otherwise.
	 * 
	 * @param value
	 *            the value to lookup.
	 * 
	 * @return <code>true</code> if the range contains the specified value.
	 */
	public boolean contains(double value) {
		return (value >= this.lower && value <= this.upper);
	}

	/**
	 * Returns <code>true</code> if the range intersects with the specified
	 * range, and <code>false</code> otherwise.
	 * 
	 * @param b0
	 *            the lower bound (should be <= b1).
	 * @param b1
	 *            the upper bound (should be >= b0).
	 * 
	 * @return A boolean.
	 */
	public boolean intersects(double b0, double b1) {
		if (b0 <= this.lower) {
			return (b1 > this.lower);
		} else {
			return (b0 < this.upper && b1 >= b0);
		}
	}

	/**
	 * Returns <code>true</code> if the range intersects with the specified
	 * range, and <code>false</code> otherwise.
	 * 
	 * @param range
	 *            another range (<code>null</code> not permitted).
	 * 
	 * @return A boolean.
	 * 
	 * @since 1.0.9
	 */
	public boolean intersects(Range range) {
		return intersects(range.getLowerBound(), range.getUpperBound());
	}

	/**
	 * Returns the value within the range that is closest to the specified
	 * value.
	 * 
	 * @param value
	 *            the value.
	 * 
	 * @return The constrained value.
	 */
	public double constrain(double value) {
		double result = value;
		if (!contains(value)) {
			if (value > this.upper) {
				result = this.upper;
			} else if (value < this.lower) {
				result = this.lower;
			}
		}
		return result;
	}

	/**
	 * Creates a new range by combining two existing ranges.
	 * <P>
	 * Note that:
	 * <ul>
	 * <li>either range can be <code>null</code>, in which case the other range
	 * is returned;</li>
	 * <li>if both ranges are <code>null</code> the return value is
	 * <code>null</code>.</li>
	 * </ul>
	 * 
	 * @param range1
	 *            the first range (<code>null</code> permitted).
	 * @param range2
	 *            the second range (<code>null</code> permitted).
	 * 
	 * @return A new range (possibly <code>null</code>).
	 */
	public static Range combine(Range range1, Range range2) {
		if (range1 == null) {
			return range2;
		} else {
			if (range2 == null) {
				return range1;
			} else {
				double l = Math.min(range1.getLowerBound(), range2
						.getLowerBound());
				double u = Math.max(range1.getUpperBound(), range2
						.getUpperBound());
				return new Range(l, u);
			}
		}
	}

	/**
	 * Returns a range that includes all the values in the specified
	 * <code>range</code> AND the specified <code>value</code>.
	 * 
	 * @param range
	 *            the range (<code>null</code> permitted).
	 * @param value
	 *            the value that must be included.
	 * 
	 * @return A range.
	 * 
	 * @since 1.0.1
	 */
	public static Range expandToInclude(Range range, double value) {
		if (range == null) {
			return new Range(value, value);
		}
		if (value < range.getLowerBound()) {
			return new Range(value, range.getUpperBound());
		} else if (value > range.getUpperBound()) {
			return new Range(range.getLowerBound(), value);
		} else {
			return range;
		}
	}

	/**
	 * Creates a new range by adding margins to an existing range.
	 * 
	 * @param range
	 *            the range (<code>null</code> not permitted).
	 * @param lowerMargin
	 *            the lower margin (expressed as a percentage of the range
	 *            length).
	 * @param upperMargin
	 *            the upper margin (expressed as a percentage of the range
	 *            length).
	 * 
	 * @return The expanded range.
	 */
	public static Range expand(Range range, double lowerMargin,
			double upperMargin) {
		if (range == null) {
			throw new IllegalArgumentException("Null 'range' argument.");
		}
		double length = range.getLength();
		double lower = range.getLowerBound() - length * lowerMargin;
		double upper = range.getUpperBound() + length * upperMargin;
		if (lower > upper) {
			lower = lower / 2.0 + upper / 2.0;
			upper = lower;
		}
		return new Range(lower, upper);
	}

	/**
	 * Shifts the range by the specified amount.
	 * 
	 * @param base
	 *            the base range (<code>null</code> not permitted).
	 * @param delta
	 *            the shift amount.
	 * 
	 * @return A new range.
	 */
	public static Range shift(Range base, double delta) {
		return shift(base, delta, false);
	}

	/**
	 * Shifts the range by the specified amount.
	 * 
	 * @param base
	 *            the base range (<code>null</code> not permitted).
	 * @param delta
	 *            the shift amount.
	 * @param allowZeroCrossing
	 *            a flag that determines whether or not the bounds of the range
	 *            are allowed to cross zero after adjustment.
	 * 
	 * @return A new range.
	 */
	public static Range shift(Range base, double delta,
			boolean allowZeroCrossing) {
		if (base == null) {
			throw new IllegalArgumentException("Null 'base' argument.");
		}
		if (allowZeroCrossing) {
			return new Range(base.getLowerBound() + delta, base.getUpperBound()
					+ delta);
		} else {
			return new Range(shiftWithNoZeroCrossing(base.getLowerBound(),
					delta),
					shiftWithNoZeroCrossing(base.getUpperBound(), delta));
		}
	}

	/**
	 * Returns the given <code>value</code> adjusted by <code>delta</code> but
	 * with a check to prevent the result from crossing <code>0.0</code>.
	 * 
	 * @param value
	 *            the value.
	 * @param delta
	 *            the adjustment.
	 * 
	 * @return The adjusted value.
	 */
	private static double shiftWithNoZeroCrossing(double value, double delta) {
		if (value > 0.0) {
			return Math.max(value + delta, 0.0);
		} else if (value < 0.0) {
			return Math.min(value + delta, 0.0);
		} else {
			return value + delta;
		}
	}

	/**
	 * Scales the range by the specified factor.
	 * 
	 * @param base
	 *            the base range (<code>null</code> not permitted).
	 * @param factor
	 *            the scaling factor (must be non-negative).
	 * 
	 * @return A new range.
	 * 
	 * @since 1.0.9
	 */
	public static Range scale(Range base, double factor) {
		if (base == null) {
			throw new IllegalArgumentException("Null 'base' argument.");
		}
		if (factor < 0) {
			throw new IllegalArgumentException("Negative 'factor' argument.");
		}
		return new Range(base.getLowerBound() * factor, base.getUpperBound()
				* factor);
	}

	/**
	 * Tests this object for equality with an arbitrary object.
	 * 
	 * @param obj
	 *            the object to test against (<code>null</code> permitted).
	 * 
	 * @return A boolean.
	 */
	public boolean equals(Object obj) {
		if (!(obj instanceof Range)) {
			return false;
		}
		Range range = (Range) obj;
		if (!(this.lower == range.lower)) {
			return false;
		}
		if (!(this.upper == range.upper)) {
			return false;
		}
		return true;
	}

	/**
	 * Returns a hash code.
	 * 
	 * @return A hash code.
	 */
	public int hashCode() {
		int result;
		long temp;
		temp = Double.doubleToLongBits(this.lower);
		result = (int) (temp ^ (temp >>> 32));
		temp = Double.doubleToLongBits(this.upper);
		result = 29 * result + (int) (temp ^ (temp >>> 32));
		return result;
	}

	/**
	 * Returns a string representation of this Range.
	 * 
	 * @return A String "Range[lower,upper]" where lower=lower range and
	 *         upper=upper range.
	 */
	public String toString() {
		return ("Range[" + this.lower + "," + this.upper + "]");
	}

}
